Field of the Invention
The present invention relates to a diagnostic device for the in vivo and/or in vitro detection of a bio marker in a fluid or tissue comprising a binding agent that specifically binds said bio marker, a linker compound, and a substrate composed of a metallic, a semiconductor, or a polymeric carrier, wherein the binding agent is an enzyme inhibitor. The present invention further relates to a method for detecting bio markers in a fluid or tissue using the diagnostic device of the invention, as well as kits for detecting disease related bio markers comprising the diagnostic device of the invention. The invention further relates to the use of said binding agents for the detection of specific disease-related target structures.
Many bio markers, such as specific cell types, small molecules, bacteria, and viruses are present in human bodily fluids. However, due to their low concentrations, they are not detectable in an efficient way by the use of known enrichment methods, so they cannot be used for conventional diagnostic methods, such as detection methods established in clinical chemistry, pathology, and cytology.
Bio markers, for example circulating tumor cells present in a blood sample are detected in vitro by commercially available methods using immunocytochemical approaches. Antibodies specific to epithelial antigens such as CK or EpCAM are generally the most widely used markers for epithelial tumor cell detection despite variable rates of false-positive and -negative staining. For instance, the percentage of CK-positive cells in normal controls range from 0 to 20% in instances of non-specific binding of non-tumoural cells or in instances of specific binding to circulating epithelial cells, which are present due to trauma or inflammation within the body. Due to non-specific binding, specificity is limited, and the sample volume necessary for the detection of the bio marker is very high. Furthermore, antibody-based techniques involve high costs for preparing the antibody necessary for detection.
A further drawback of antibody-based techniques is that the antibody can only be removed from the antigen under strong conditions (with respect to high salt conditions, heat, pH-value) which is highly detrimental for the cell. In contrast, the binding agent of the invention may be easily resolved in high concentrations under normal conditions, thereby releasing the binding agent bound to the linker. Therefore, these techniques are less suitable for in vitro detection of biomarkers.
Therefore, there is a need in alternative diagnostic devices which do not have the drawbacks of the detection devices and methods known in the art.